HISTORY OF WHALES 



37 



rather than antecedent to the line of 

 development that led to the telescoped 

 condition of the braincase seen in skulls 

 of typical cetaceans. On the contrary it 

 is more probable that they are collateral 

 derivatives of the same stock from which 



cetaceans. Miller (1913) holds that the 

 known zeuglodonts are not directly an- 

 cestral to any of the recent whales, and 

 contends that the transition from this type 

 of skull to the toothed whale (Od ontoceti) 

 skull involves simpler principles than is 



x" 





. ...;**" 



i - 



: . ; 



' - /■- 



I L 



PRDTOCETUS ATAVUS Fraas 

 Lower Middle Eocene -Fayum Egypt 



y-r-r r 



Fig. 1. Skulls of Zeuglodonts 



A. Dorsal and ventral views of skull of Protocetus atavus (after Fraas). B. Lateral and posterior views of 

 skull of Prozeuglodon stromeri (after Stromer). 



the true Cetacea sprang. No tendency 

 toward cranial telescoping has been 

 observed in any of the zeuglodonts, yet 

 they possess certain structural features 

 which are morphologically intermediate 

 between early land mammals and true 



the case for the whalebone (Mysticeti) 

 whales. Curiously enough, periotic 

 bones of both the whalebone and the 

 toothed whale types have been found 

 attached to skulls of zeuglodonts. 

 The bones in the rostrum and cranium of 



